Well, I couldn't wait to find out the proper way to yank it all apart...so I just made it up as I went along :-)
I still remember the first time I ever did a clutch and flywheel job on a car, it was about ten years ago on my Audi quattro. I was so nervous about such a 'big and scary' job, I called in my friend Eddy to give me a hand. (well, actually to do the job while I watched/helped). When it comes to vehicles, the inside of a transmission was my "final frontier". It's the only part of the car that still scares me to touch. I can build and rebuild motors, tear apart anything else, but a transmission? Those always seemed complex and scary. Plus, the factory manuals usually list about 17 different specialty tools you have to have!
Well, I have to say, after laying out the insides of the Porsche transmission in my garage...they're no longer scary. In fact, I'm kind of disappointed I don't have the parts or funds to rebuild the syncros and gear stack on this one...just look at it sitting there, crying out for a full tear down ;-) A full transmission rebuild is in my plans for the next year, just out of plain curiosity!
Getting into the Porsche 901 wasn't so bad. I suspect there is an ideal gear to have selected when one goes to dismantle the transmission. Mine was in an unknown gear with the main shift rod dislodged. Once I pulled the gear cluster out halfway, I was able to move the shift rod around enough to pop the whole unit out of the transmission. I did almost need three hands to do it, but eventually I got it.
My gear stack checked out about as well as I expected. The first gear syncro teeth are in poor shape, which I expected from reading so many threads about the 901. Fifth gear is worn as well, but the others look relatively good. The pinion gear looked quite good so I wasn't going to bother pulling the diff. Instead I figured I'd do a quick check through the input shaft hole. As I was rotating the diff around one of these two pieces came into view...(battery for scale)
That would be the remains of an input shaft seal. Apparently at some point in this transmission's life someone drove an old seal into the transmission instead of removing it properly. It also explains the metal fragments I found on the drain plug!
Needless to say, I decided I would empty the case and clean out anything and everything.
Reassembly is fairly straight forward. I followed another thread which said to put the transmission in neutral. It was a relatively easy job getting the gear stack in, and I was pretty sure I checked the main shift rod before moving forward. What I should have done, however, was also check each of the other shift rods to ensure they were still in neutral. Either while sliding the gear stack in, or while putting the nose cone on, I managed to select reverse gear on the transmission. The main shift rod was not in the correct spot though so once it was all buttoned up I had reverse, or a locked up transmission when selecting 'any gear'. I realized I was getting two gears at once, and popped off the side cover/support. From there I could see reverse was selected but the main shift rod wasn't in the right spot. Took a bit of finesse, but I managed to get it shifted back into neutral and sorted without cracking open the transmission again.
At least now I can use continue to modify my pan to fit and then I'll decide whether or not I want to do a full rebuild on the trans. I will probably run it as-is for a bit, so I can see how I like the gear ratios with my engine. If I'm going to do a rebuild I might as well make sure it's got the ideal gearset!
-Dave